The Dual Role of the Neonatal Fc Receptor (FcRn) in Podocytes

新生儿 Fc 受体 (FcRn) 在足细胞中的双重作用

• 批准号: 9117538
• 负责人: JUDITH T., BLAINE
• 金额: $ 31.1万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2020-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9117538
• 关键词: Active Biological Transport; Albumins; Animals; Antibodies; Antigen Presentation; Antigen-Antibody Complex; Antigens; Area; Attenuated; Blood Volume; CD4 Positive T Lymphocytes; Cell Communication; Cells; Complex; Coupled; Data; Dendritic Cells; Development; Disease; Disease Progression; Endothelial Cells; Exposure to; Filtration; Glomerular basement membrane antibody; Glomerulonephritis; Health; Human; Imaging Techniques; Immune; Immunoglobulin G; Kidney; Kidney Diseases; Kidney Failure; Knock-out; Knockout Mice; Knowledge; Lead; Lysosomes; MHC Class II Genes; Mediating; Microscopy; Modeling; Molecular; Nephritis; Nephrotic Syndrome; Pathway interactions; Process; Proteins; Proteinuria; Proteolytic Processing; Renal glomerular disease; Role; Serum Proteins; Severities; Severity of illness; T-Cell Activation; T-Lymphocyte; Time; Tubular formation; Up-Regulation; Work; base; cell type; clinically relevant; design; effective therapy; glomerular basement membrane; glomerular filtration; glomerulosclerosis; in vivo; in vivo Model; intravital microscopy; macromolecule; mouse model; neonatal Fc receptor; podocyte; prevent; protein transport; slit diaphragm; targeted treatment; trafficking; transcytosis; uptake

 DESCRIPTION (provided by applicant): In the normal kidney, an enormous volume of blood (180 L) is filtered each day through the glomerular filtration barrier. By even the most conservative estimates, between 1 - 3 g of albumin a day make it through the filtration barrier. Podocytes are a key part of the GFB and the molecular basis of protein trafficking in podocytes is unknown. In preliminary studies, we have found that podocytes actively transcytose two major serum proteins, albumin and immunoglobulin G (IgG), and that transcytosis is the major pathway for handling these proteins. We have also found that trafficking of IgG is more complicated than that of albumin and that podocytes direct trafficking of IgG differently depending on whether IgG is coupled to antigen. In other cell types such as renal tubular cells and endothelial cells, the neonatal Fc receptor (FcRn) is required for transcytosis of albumin and IgG. In dendritic cells, FcRn is required for antigen/IgG (immune complex) trafficking to the lysosome for antigen presentation on MHC Class II. Based on our preliminary studies and the known role of FcRn in other cell types we propose a dual role for FcRn in podocytes. Specifically, we hypothesize that (1) FcRn is required for transcytosis of albumin and IgG through the podocyte and (2) FcRn is required for immune complex presentation in podocytes by directing antigen/IgG complexes to the lysosome for processing and presentation in podocyte MHC II. In this proposal, we will use primary podocytes isolated from wild type and FcRn knockout mice to determine whether FcRn is required for transcytosis of albumin and IgG. We will also determine whether the glomerular sieving coefficient for albumin and IgG is significantly less in wild type versus FcRn knockout mice and whether podocyte-specific knockout of FcRn in vivo leads to protein accumulation within the glomerulus and glomerulosclerosis. We will examine whether FcRn is required to direct antigen/IgG complexes to the lysosome for degradation and antigen presentation on podocyte MHC Class II and determine whether lack of FcRn abrogates antigen/IgG presentation in podocytes. Finally, we will determine whether podocyte-specific knockout of FcRn ameliorates disease in a mouse model of immune-mediated nephritis. We will also use intravital multiphoton microscopy, a dynamic advanced imaging technique, to examine whether podocyte-specific knockout of FcRn reduces T retention times within the glomerulus after induction of immune-mediated nephritis. The work outlined in this proposal is significant because it is the initial step in understanding exactly how serum proteins are trafficked through the podocyte. Protein accumulation in podocytes has been shown to be toxic to podocytes and correlates with podocyte loss and glomerulosclerosis. Knowledge at the molecular level of how proteins are handled by the podocyte will form the basis for the design of rational therapies to prevent protein accumulation in podocytes. An understanding of the dual role of FcRn in podocytes (both in transcytosis and antigen presentation) is also critical to the design of safe and effective therapies to treat immune-mediated glomerular diseases.

 描述（由适用提供）：在正常肾脏中，每天通过肾小球滤过屏障每天过滤大量的血液（180升）。即使是最保守的估计，每天的白蛋白在1-3克之间使其通过过滤屏障。足细胞是GFB的关键部分，并且在足细胞中蛋白质运输的分子基础尚不清楚。在初步研究中，我们发现足细胞积极地跨膜蛋白，白蛋白和免疫球蛋白G（IgG），而转胞胞病是处理这些蛋白质的主要途径。我们还发现，IgG的运输比白蛋白的运输更为复杂，并且根据IgG是否与抗原耦合，对IgG的Podocytes直接运输IgG的直接运输也有所不同。在其他细胞类型（例如肾小管细胞和内皮细胞）中，新生儿FC受体（FCRN）是白蛋白和IgG的转胞胞毒所必需的。在树突状细胞中，抗​​原/IgG（免疫复合物）运输到溶酶体中需要FCRN，以在MHC II类上进行抗原表现。根据我们的初步研究和FCRN在其他细胞类型中的已知作用，我们提出了FCRN在足细胞中的双重作用。具体而言，我们假设（1）FCRN是通过足细胞转胞胞毒素和IgG需要的，并且（2）FCRN是通过将抗原/IgG复合物引导到溶酶体的Podocyte MHC MHC II中的溶酶体来引导和表现的Podocytes中的免疫复合物表现。在此提案中，我们将使用从野生型和FCRN敲除小鼠中分离出的原发性足细胞来确定是否需要FCRN来进行白蛋白和IgG的转胞细胞增多。我们还将确定在野生型和FCRN敲除小鼠中，白蛋白和IgG的肾小球筛分系数是否明显降低，以及FCRN的Podocyte特异性敲除体内的fcrn oft型敲除，是否会导致肾小球和肾小球硬化症中的蛋白质在体内积累。我们将检查是否需要FCRN将抗原/IgG复合物引导到溶酶体上，以降解和抗原呈现Podocyte MHC II类，并确定是否缺乏Podocytes中的FCRN抗原/IgG表现。最后，我们将确定在免疫介导的肾炎的小鼠模型中，FCRN的足细胞特异性敲除可以改善疾病。我们还将使用动态的高级成像技术使用浸润性多光子显微镜检查FCRN的足细胞特异性敲除是否会在诱导免疫介导的肾炎引起后肾小球内的t保留时间。该提案中概述的工作非常重要，因为它是确切理解血清蛋白如何通过足细胞运输的第一步。足细胞中的蛋白质积累已被证明对足细胞有毒，并且与足细胞丧失和肾小球硬化有关。在分子水平上的知识对蛋白质如何处理蛋白质将构成设计理性疗法以防止蛋白质积累在足细胞中的基础。对FCRN在足细胞中的双重作用的理解（在胞胞菌和抗原表现中）对于设计安全有效的疗法以治疗免疫介导的肾小球疾病也至关重要。